Julius Caesar Ibbetson (1759-1817)is credited with the invention of ‘Gumption’, a mastic-based painting medium (Carlyle 2001 pp.106-8); see also Ibbetson’s book An Accidence or Gamut of Painting in Oil and Water Colours, 2nd ed., 1828 with a recipe for Gumption (transcribed in Rotha Clay, Julius Caesar Ibbetson 1759-1817, 1948, p.138; see also pp.85-6). The medium was used by Sir George Beaumont.